Bulldog coupler complete bolt failure !

[John E Davies]

EDIT 08/29/19 Added extra bolts to the coupler here: ...https://olivertraveltrailers.com/topic/how-to-reinforce-your-bulldog-coupler-by-adding-extra-bolts/

 

 

Please comment ... I am worried. Here is what I submitted to Service:

 

Hi, I recently replaced my coupler with a larger one. I used new 1/2"-18 Grade 8 bolts and torqued them to the specified 80 ft lbs. That is the recommended value here:

tsb-torque-specifications/

And it is also the recommended value, generically, for this bolt type and size. HOWEVER, the Bulldog instructions recommend installing Grade 5 bolts at 55 ft lbs.

Bulldog Instr

Today I went to check the bolt torques, and one of my Grade 8 ones sheared and flew across the room. The other bolt is fine. So either I just got one bad bolt, or the torque value is not appropriate for this application, or I should be using SOFTER, less brittle Grade 5 bolts as recommended by Bulldog, at a smaller torque value.

I think you need to amend your TSB with detailed instructions on type of bolt to be used and the torque value. Somebody has, or is going to, replace his hardware using the Bulldog instructions and your higher TSB torque value, you can bet one it.,.... I also think this merits a new TSB and an email to all owners to clarify the situation.

Please advise, should I just put in two new Gr 8 bolts at 80 ft lbs or go with Gr 5 at 55 ft lbs?

Also, I want to install a third bolt half way between the two factory locations, to add some strength and a safety factor in case one fails. Is it OK to drill new holes up high, so the bolt runs just under the top inside surface of the tongue? I would not use a compression sleeve.

John Davies

Spokane WA

[BackofBeyond]

JD, Its difficult to determine the quality of the failed bolt, but certainly is an important aspect of your problem. Its been my experience that the softer grade 5 have a better stretch tolerance, than the harder grade 8. I broke many 8's on my brush hog, change to the softer metals, much better. Sometimes in our efforts to make stuff better, beefier, we inadvertently go backwards.

 

I don't know what Oliver will say, but the quoted Bulldog instructions are clear. Good luck on your quest.

 

 

[Overland]

If the standard torque for those bolts is 80, then that’s exactly what Oliver should recommend. The bolts aren’t under any tension other than what you’ve applied so it can’t be the application. And the bolt has obviously been twisted in two, not sheared

 

You either got a bad bolt or you over torqued it. If it were me, I’d get your torque wrench calibrated to eliminate the latter possibility.

[Overland]

Taking a look at your thread on replacing your coupler, I see that you used anti seize on the bolts. I’ve always been told that when you do that you have to lower your torque setting by 20%. So that’s possibly the answer.

[Overland]

I’ve been looking around to see if I can find anything authoritative on how much to reduce torque values when using anti seize, but I haven’t found anything yet but forum posts. This particular post I found was interesting - 50% reduction for Teflon based anti seize. Wow.

LUBRICANT OR PLATING TORQUE CHANGES

Oil, Reduce torque 15% to 25%

Dry Film (Teflon or moly based), Reduce torque 50%

Dry Wax (Cetyl alcohol), Reduce torque 50%

Chrome plating, No change

Cadmium plating, Reduce torque 25%

Zinc plating, Reduce torque 15%

[rideandfly]

John,

 

We had several failures with grade 8 bolts on one industrial application and found the bolts were torqued wet (oil used) at the dry  torque value, Never Seize would probably have the same results as oil, if used. This was several years ago, but must have been the same bolt size because remember 80FT LBS dry for that application.  Once we started torquing dry threads the issue went away.

 

If you go with Bulldog's recommended grade 5, would torque to the dry value with dry threads.

[John E Davies]

I use Permatex silver anti-seize and it specifically says on the can to NOT reduce the torque setting. Maybe that is incorrect....! But I have used it for many decades and never had a problem like this before. Here is the TDS:

 

 

I am not new at this, it is not a problem with the installation. Maybe my wrench is off, but if so, then it would have to be WAY off to snap a big Grade 8 bolt. It didn't't feel like it was twice the recommended value... I have used it on lug nuts etc and there are no issues... it feels fine during use.

 

I intentionally snapped a 1/2" stainless bumper bolt that was seized. That is a softer material, and it required a two foot breaker bar and a whole lot of grunt to twist it apart.  I think I am looking at a bad Grade 8 bolt. Which is disappointing since it came from Fastenal, not the hardware store.

 

Thanks for the comments. It will be very interesting to see what Howenwald advises.

 

John Davies

 

Spokane WA

 

 

 

 

[rideandfly]

Which is disappointing since it came from Fastenal, not the hardware store.

 

John,

 

Our Grade 8 failures were with Fastenal, too.  Permatex Anti Seize is a lubricant.

 

This statement from the following link:

 

"Torque-Tension Relationship"

 

" When applying an anti-seize to your components, the torque value to achieve the same clamp load will be lower. If anti-seize is used with the torque specified for a dry assembly, you risk exceeding the proof load of the fastener."

 

https://www.manufacturing.net/article/2013/04/understanding-true-value-anti-seize

[Overland]

Yeah, I think it's just common sense that if you grease a bolt, you'll need less torque to achieve the desired tension.  The only question for me is what % reduction should you use.

 

I guess another question would be why use the stuff on bolts you don't plan to remove.  It's great for spark plugs, but the one job of the nut on a coupler bolt is to not come off.  Those nuts aren't too bright, so I don't want to make their job any harder than it needs to be.

 

I don't know what to make of their "normal torque values".  Maybe they mean normal wet torque values.  Regardless, I think your own experience proves them wrong.  If you really want to test it out, buy several bolts and test them to failure both with and without the grease.  Then you'll know exactly how much to lower your torque value.

[rideandfly]

John had it right @ 80 FT LBS,

 

Found the Fastenal Torque Value calculator:

 

SAE J429 Grade 8  bolt 1/2" coarse thread:

 

Recommended torques:  79.8 FT LBS WET    106.4 FT LBS Dry  

 

https://www.fastenal.com/en/83/torque-calculator

[Overland]

If that’s the case, then I go back to my original post - it’s either the bolt or the wrench.

 

In any case, I don’t see how it’s an Oliver problem. This is an interesting and potentially valuable thread, but I really wish it had a less sensational title and first post.

[John E Davies]

Overland, it isn’t sensational, it is a safety issue, if the coupler manufacturer recommends one part, and Oliver substitutes a different part, and the torque values are different, it will cause problems. An owner may put in Grade 5 bolts and overtighten them because of the vague Oliver torque recommendation which never mentions the type of bolt. Whether or not my snapped bolt was a fluke is not the issue, it’s the need to establish which bolts are supposed to be used here.

 

What was sensational was having that heavy bolt go bang and shoot at high speed across my garage. That is not something you want to happen during a trip.

 

John Davies

Spokane WA

[Overland]

John, it's sensational because you're trying to imply that it is somehow Oliver's fault that you either bought a bad bolt or overtorqued one when doing your own modifications. Oliver is not to blame for recommending what you yourself agree is the correct torque. Oliver's torque specifications are not vague, because they're intended for the bolts installed at the factory, or like for like replacements, and those are Grade 8.

 

 

[Overland]

Continuing the discussion on anti seize and torque, I ran across this diagram just now on boltscience.com:

 

 

What caught my eye is the proportion of friction attributed to the nut face, rather than the threads. I'm going to guess that values for wet torque assume that the lubricant is only on the threads themselves and not the face of the nut. Maybe I'm wrong, but that would be my assumption - meaning that if you get too much anti seize on the threads and it squeezes onto the face of the nut, it could really alter the amount of torque needed to tighten the bolt. I've no idea if that's the case with John's bolt (is the silver on the bolt face from abrasion or is it aluminum from the anti seize?) but it's something to consider.

[WhatDa]

There are a lot of reasons a torque wrench can be off. Even 10lbs over probably shouldn't lead to strain failure, but wrench variation+lubrication form the Permetex+maybe not good bolts could lead there. The snap-on man can calibrate or verify calibration (and sell you a nice wrench), or if you can fix a fastener in place (or use something already torqued over 80 foot lbs) and hang an appropriate weight off the handle to approximate 80 foot-lbs. You can also use a luggage scale to measure the force - subject to the accuracy of that scale. Tau=rxF.

[Raspy]

I found that when replacing my Bulldog coupler with the 2 5/16" model, that the bolts as installed from Oliver had bottomed out in the nuts before clamping sufficiently. This meant that almost all of the torque was going into twisting the bolt, rather than tensioning it.

 

With insufficient clamping force, the holes in the Bulldog coupler had begun to elongate. A couple of grade 8 washers added to each bolt,fixed that problem.

 

Lubing the bolt thread with either grease or anti-seize increases the tension on the bolt with any given torque value on the nut.

 

In the case of engine head studs, for instance, the bolts are clamping the head to the engine, and bolt stretch is the best way of arriving at the design clamping force. Nut torque is just an easy way to get there without special tools, but not exact.

 

In the case of the bulldog coupler, we need bolt tension and we need shear strength. The shear is more determined by the bolt hardness and diameter, while the tension is determined by the nut torque. In a perfect world, we'd get the bolt stretch specs and go for that by adjusting the nut torque. But in the real world, we use nut torque. It never is clear how much we should reduce the torque based on the affect of the thread lubrication. But it is clear that lubing the threads increases the tension.

 

It may be that John had a defective bolt. It may also be that any problem with the bolt was made more obvious by lubing the threads, which increased the tension while torquing. It may also be that there was an unfair percentage of torque going into twisting the bolt because of the threads bottoming, or nearing the end of the threaded section.

 

Since those bolts are not designed to be removed frequently, and since they are plated for corrosion, and since they may have been defective, I'd replace them and install them with no lube, while making sure the threads are not bottoming. We want the unthreaded shank to carry the shear load, so get bolts that have a long enough unthreaded length. Then add grade 8 flat washers to make sure the nut does not bottom before reaching full torque.

 

If you have two torque wrenches, work them against each other on a nut and bolt, to see if they agree on their torque values. If not, get the best one calibrated or replace one of them. But really, the torque should not have to be very precise to work properly in this case. If the bolt is near it's full capacity, upsize it. It seems grade 8 is a good choice for the bolts because they are primarily in shear, but I'm not an expert on the differences between grade 5 and grade 8 in that regard. The torque is just a way to keep things from moving around while under load.

[BackofBeyond]

Crap fastener infiltration into the USA

 

Like many I tend to "hope" the products I purchase from known suppliers - like a Fastenal- are better quality -but unfortunately, it appears quality cannot be inferred by the supplier - sad.

I use thread lock and never thought about the reduction of torque values - so I learned something here. But I never had a failure either.

 

Were I JD, I would likely replace the bolts, and go at it again. Might do a failure test - may even use a thread lock nut. A fastening engineer, and I've had way to much experience with their "type" :-), would probably start at the calibration and lube issue, then go into some sort of bolt/nut investigation, an on on on on....

Just replace it, and check it regularly is my SOP.

Like others, I don't know why Oliver would respond, not their problem, this was a customer installed upgrade.

 

A sensational header would be something like - Warning! Bulldog coupler bolt failure! - Oh wait, that's what I thought was the subject when I first clicked.... Oh well we all know better now. Thanks JD, I did learn something here. keep us in the loop.

[John E Davies]

Like others, I don’t know why Oliver would respond, not their problem, this was a customer installed upgrade.

A sensational header would be something like – Warning! Bulldog coupler bolt failure! – Oh wait, that’s what I thought was the subject when I first clicked…. Oh well we all know better now. Thanks JD, I did learn something here. keep us in the loop.

 

Oliver uses these exact bolts at the factory, the hardware was not an upgrade. Some of their installations, like mine, did not have enough washers under the nuts.  I only replaced like for like. But my relacememt nuts had enough washers.

 

I did contact Bulldog, and they said that Grade 5 was plenty good, Grade 8 was also acceptable. I reworked mine with Grade 5 bolts (and Grade 8 washers and nuts) since I think one issue is that when the poorly formed sides of the coupler are squeezed together, they do not mate perfectly with the tongue, and the nut and bolt head experience a bending force. The one that did not snap showed NO signs of distress or stretched threads (which would have indicated over-torquing) but it did have a slight bend at the threads.

 

I added two more short bolts with the nuts inside the tongue. I reduced the torque value by 20% due to the discussion here, but I do not think that was the problem in the first place. I can't recall the last time I busted a bolt or stud during installation....

 

 

 

I'll start a new thread about this mod when I get the time. I do think that additional hardware is a good safety factor, that might prevent a call to AAA if you have a failure on a trip. Thanks everyone, for your patience and participation. I have sent Oliver Service some pictures for their examination. Maybe they will consider adding a third sleeve and through bolt. And bigger would be better...

 

John Davies

 

Spokane WA

 

 

 

 

[sailorashore]

John Davies

Thank you for the report and pictures. For some time I have been thinking about adding an extra bolt to the coupler-tongue assembly. Drill a 1/2” hole vertically through the top of the coupler and install bolt about where the letters “FT” show up in your first photograph. Can you think of a reason why this would be a bad idea/wouldn’t work? Please advise.

John Shkor

SailorsAshore

[John E Davies]

Drill a 1/2” hole vertically through the top of the coupler and install bolt about where the letters “FT” show up in your first photograph. Can you think of a reason why this would be a bad idea/wouldn’t work? Please advise.

 

I actually considered that a couple of years ago. The basic problem is that there is an air gap between the top of the frame and the bottom of the coupler. The coupler is crudely formed so it relies on the clamping force against the sides of the tongue. I felt that extra side force was better engineering than adding extra hardware at 90 degrees to it. The frame would likely distort unless you added an extra plate underneath or bedded the coupler in epoxy. There isn’t room for a plate due to the compression sleeves being in the way. Bedding it would be OK if you applied a release agent to the frame. But it might trap water, which would be very bad.

 

John Davies

Spokane WA

[Raspy]

John,

I like your way of adding two extra bolts. It is better than only one on top and you avoided the pinching problem on the tongue by using two short bolts instead of one long through bolt. Nice job.

[sailorashore]

John Davies:

Got it. Makes sense. Will use side bolts.

John Shkor SailorsAshore

[connor77]

I know this is an older thread but would there ever be an instance where a 2" ball/coupler would be preferred, better or necessary vs the 2 5/16"?  I've read all of the threads related to John's coupler modifications and did a quick bulldog price check of 2" vs 2 5/16" and the difference is $20

I have a long wait for my Oliver (June 2021) but this is one modification I'm planning to do.  Unless there is a reason why a user would actually need the smaller bulldog I don't understand why Oliver wouldn't install the larger one on all units.  What am I missing aside from 2" is a more common/available size?

For reference, I have a 2020 Tundra and, from everything I've read, my towing experience will be considerably better with the weight distribution hitch which I'm planning to purchase.  Ultimately, I'd like a diesel tow vehicle ($$$) but that will have to wait a while.

[topgun2]

I think you got to the nub of the issue - the 2" is more common.  I would add that given the size and weight of the Oliver, the 2" Bulldog is more than adequate for the vast majority of people.

Your 2020 Tundra is certainly a nice truck and will tow the Oliver well.  You might want to check though - I'm guessing that the weight distribution hitch is required in order for you to maintain your warranty by Toyota - Ford, GM and Dodge all require it for 1/2 ton trucks.

Bill 

[Geronimo John]

On 8/26/2019 at 3:51 AM, Raspy said:

f you have two torque wrenches, work them against each other on a nut and bolt, to see if they agree on their torque values.

But just don't do this on your wet bolts with splines.  A great way to spin the splines off.  Can't say for the shackles, but for the EZ flex it will result in the center bolt walking out of it's desired home.  There are ancient threads on this topic.  

GJ